SAP troubles

[maspen]

Hello,

I got a serious problem with Session Announcement Protocol.

We stream about 15 mpeg2 streams over a LAN in multicast.
On the client side, VLC is used on XP atom based stations to view programs, which are announced via SAP on the default multicast group.
We use 3com 4500G switch as core switch, and 4500 on the end side. Between, a 1GB fibber should be enough for the 15 streams.
Multicast and IGMP snooping are both enabled on all switches.

When a few client are watching programs, everything just work fine. No multicast storm, no problem...

But on mid/heavy load, the SAP list of programs randomly scroll up, disappear, and we have to re select the desired program.
Sniffing with wireshark, it's appears that for some reason, we lost the sap membership, and SAP announces are not received for a period from 10 to 30 seconds.
Could someone explain to me why does the list disappear, as the expiry time with the default value of 1800s should keep list integrity within this timeout ?
I tried to change value with no success.
I precise that IPV6 is deactivated, as recommendation says.

Thanks a lot by advance

[Rémi Denis-Courmont]

Loosing membership is a problem between the IP stack and the routers. Not much help to expect from a VLC forum.

[maspen]

First, thank you for answer.

I know that, but why vlc does not maintain the playlist, as it is reconstructed instantaneously, and not at the en of the timeout of 1800s ?